Improve recovery from compile-time errors.

pkg/front_end/lib/src/fasta/builder/library_builder.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library fasta.library_builder;
 
 import '../combinator.dart' show Combinator;
 
-import '../errors.dart' show InputError, internalError, printUnexpected;
+import '../errors.dart' show internalError;
 
 import '../export.dart' show Export;
 
 import '../loader.dart' show Loader;
 
 import '../messages.dart' show nit, warning;
 
 import '../util/relativize.dart' show relativizeUri;
 
 import 'builder.dart'
@@ skipping 11 matching lines @@
   final Scope scope;
 
   final Scope exports;
 
   final ScopeBuilder scopeBuilder;
 
   final ScopeBuilder exportScopeBuilder;
 
   final List<Export> exporters = <Export>[];
 
-  final List<InputError> compileTimeErrors = <InputError>[];
-
   final Uri fileUri;
 
   final String relativeFileUri;
 
   LibraryBuilder partOfLibrary;
 
+  /// True if a compile-time error has been reported in this library.
+  bool hasCompileTimeErrors = false;
+
   LibraryBuilder(Uri fileUri, this.scope, this.exports)
       : fileUri = fileUri,
         relativeFileUri = relativizeUri(fileUri),
         scopeBuilder = new ScopeBuilder(scope),
         exportScopeBuilder = new ScopeBuilder(exports),
         super(null, -1, fileUri);
 
   Loader get loader;
 
   Uri get uri;
 
   Builder addBuilder(String name, Builder builder, int charOffset);
 
   void addExporter(
       LibraryBuilder exporter, List<Combinator> combinators, int charOffset) {
     exporters.add(new Export(exporter, this, combinators, charOffset));
   }
 
+  /// See `Loader.addCompileTimeError` for an explanation of the arguments
+  /// passed to this method.
+  ///
+  /// If [fileUri] is null, it defaults to `this.fileUri`.
   void addCompileTimeError(int charOffset, Object message,
-      {Uri fileUri, bool silent: false}) {
-    fileUri ??= this.fileUri;
-    if (!silent) {
-      printUnexpected(fileUri, charOffset, message);
-    }
-    compileTimeErrors.add(new InputError(fileUri, charOffset, message));
+      {Uri fileUri, bool silent: false, bool wasHandled: false}) {
+    hasCompileTimeErrors = true;
+    loader.addCompileTimeError(fileUri ?? this.fileUri, charOffset, message,
+        silent: silent, wasHandled: wasHandled);
   }
 
   void addWarning(int charOffset, Object message,
       {Uri fileUri, bool silent: false}) {
     fileUri ??= this.fileUri;
     if (!silent) {
       warning(fileUri, charOffset, message);
     }
   }
 
@@ skipping 89 matching lines @@
   /// Don't use for scope lookup. Only use when an element is known to exist
   /// (and not a setter).
   Builder operator [](String name) {
     return scope.local[name] ?? internalError("Not found: '$name'.");
   }
 
   Builder lookup(String name, int charOffset, Uri fileUri) {
     return scope.lookup(name, charOffset, fileUri);
   }
 }